Imaging menu

  Imaging parameters (filter, exposure time, number of exposures per integration) are controlled by CONFIG files. These in turn can either be recalled, or loaded via EXEC files. EXEC files specify a small program of observations and telescope operations, such as executing DARK, SKY, or OBJECT exposures, and using a series of SLIDE commands to perform a mosaic and/or dither pattern of exposures. Both of these are accessed (and executed) from within the `Imaging' menu:

• `Set_instrument' : The instrument parameters are defined by loading an instrument configuration (CONFIG) file. For example, the observer chooses the filter from a list in the instrument configuration screen and the appropriate filter combination and focus offset is automatically loaded. The exposure time must be short enough to avoid saturation (see § 5.2) and long enough to ensure that the observation is background limited for maximum sensitivity (see § 5.4); it can vary from 120ms at nbL (or as short as 12 ms if you read out a 64 64 subarray) to tens of seconds in narrow band filters. With short integration times, many exposures may be coadded by selecting a number of exposures per integration, before the data are written to disk. This saves on disk space and readout time overheads. The final image written to disk is divided by the number of exposures, thus giving an average exposure. This may be confusing as the exposure time in the header gives the total integration time (ie exposure time). The log produced at the end of the night keeps a record of the number of exposures per integration.
• `Set_EXECs' : Telescope offsets (for mosaics, etc) and sequences of different filter exposures can be specified with execution (EXEC) files. These are text files containing a list of commands to be executed in sequence by the software. A list of valid EXEC commands is given below (Table 3.5.2 in § 3.5.2). An EXEC controls how data are taken with WHIRCAM (e.g. which CONFIG to use, where the telescope points relative to the slew coordinates, whether to take an OBJECT, SKY or DARK exposure etc). This menu allows the user to define and/or edit operational EXECs. The editor for the EXEC files is EDT, so the PF1 and Enter keys become redefined as part of the EDT keypad during an EXEC edit. To exit the editor, type cntrl Z.
• `Set_observation' : This menu allows the user to define the type of observation being made (e.g. whether to execute an EXEC or a direct observation of the OBJECT, SKY, DARK etc.
• `Run' : Entering this item runs the currently defined setup (by Set_observation). Data are actually taken and stored on disk. To avoid writing rubbish to disk (and to tape), it is a good idea to add a BREAK at the beginning of every EXEC (see § 3.5.4) so that you have an oportunity to review a proposed EXEC, and to ensure that the telescope is tracking properly (especially if you are autoguiding).
• `Movies' : This menu allows you to take data in movie mode. Movie mode takes images of a pre-defined on-chip exposure time and displays them on the ALICE display without storing data to disk. \
• `Set_ALICE' : This menu allows the user to define ALICE Transputer setup parameters, such as varying the size of the array being read out.
• `Set_graphics' : This menu allows the user to change the ALICE on-line display setup. The user can change, for example, the plotting range for image display (don't attempt to change the colour table (LUT), as this can often hang), or the position and size of the statistics window on the ALICE image display. You can also specify the bad pixel mask to be applied to the display. Choose either `BPM_FPA40348_DEAD', which locates the brightest hot pixels, or `BPM_FPA40348_SAA' which locates most hot pixels, and should be used whenever taking frames in Shift+Add mode.

(Don't be too concerned if the above menu titles don't appear exactly as described, as they may change under a new release of the IRCAM3 software.)